The present invention relates generally to medical devices. More particularly, the present invention pertains to invasive surgical devices which are useful for the incision and dilation of a stenosis in the vasculature of a patient. The present invention is particularly, though not exclusively, useful for incising a stenosis with a balloon catheter blade to facilitate subsequent dilation of the stenosis.
The blockage of human arteries can lead to a variety of serious medical complications. This is so because arterial blockages reduce blood flow through the affected artery and may result in damage to the tissue that is relying on the blood supply. For example, if the blockage is in an artery which supplies blood to the heart itself, a heart attack may result.
Such arterial blockages, which are also called stenoses, are typically caused by the build-up of atherosclerotic plaque on the inside wall of an artery. In fact, several such stenoses may occur contiguously within a single artery. This can result in a partial, or even complete, blockage of the artery. As a result of the danger associated with such a blockage, several methods and procedures have been developed to treat stenoses. One such method is an angioplasty procedure which uses an inflatable balloon to dilate the blocked artery. A typical inflatable angioplasty device, for example, is disclosed in U.S. Pat. No. 4,896,669 which issued to Bhate et al. for an invention entitled xe2x80x9cDILATION CATHETERxe2x80x9d. The Bhate et al. angioplasty device includes an inflatable angioplasty balloon which is insertable into a peripheral artery of a patient for positioning across a stenosis. Once positioned, the angioplasty balloon is then inflated to flatten the stenosis against the inside wall of the artery thereby improving the blood flow through the artery.
Angioplasty balloons have enjoyed widespread acceptance in the treatment of stenoses. Recent studies, however, have indicated that the efficacy of the dilation of a stenosis is enhanced by first, or simultaneously, incising the material that is creating the stenosis. Consequently, recent developments have been made to equip angioplasty balloons with cutting edges, or atherotomes, which are intended to incise a stenosis during the dilation procedure. For example, the device disclosed in U.S. Pat. No. 5,196,024 to Barath entitled xe2x80x9cBALLOON CATHETER WITH CUTTING EDGE,xe2x80x9d which is assigned to the assignee of the present invention, is an inflatable angioplasty balloon having a number of atherotomes mounted longitudinally on the surface of the balloon.
Upon inflation of the Barath balloon, the atherotomes induce a series of longitudinal cuts into the surface of the stenotic material as the balloon expands to dilate the stenosis. As a result of such cuts, the stenosis is more easily flattened, and the likelihood of damaging the artery during dilation is reduced. Generally, however, the surface of a stenosis is bumpy and undulating, and contains numerous peaks and valleys. As such, incision of a stenosis with one long, continuous blade that is mounted on the surface of an angioplasty balloon can be uneven. Specifically, while the peaks of a stenotic surface may be effectively incised, incisions in the valleys present on the surface of the stenosis may be problematic. Thus, it can happen that only a small portion of the stenosis is actually incised. Furthermore, long, continuous blades reduce the flexibility of the catheter making it more difficult to guide the catheter through the vasculature of the patient.
In light of the above, it is an object of the present invention to provide a device for incising both the peaks and valleys of a stenosis in a vessel of a patient. It is a further object of the present invention to provide a blade unit for an angioplasty balloon having an effective cutting edge that substantially conforms to the surface of a stenosis when the balloon is inflated. It is still another object of the present invention to provide a device for incising a stenosis that is flexible enough to be easily guided through the vasculature of the patient to the site of the stenosis. It is another object of the present invention to provide a device for incising a stenosis in a vessel which is relatively simple to manufacture, is easy to use, and is comparatively cost effective.
For the present invention, a device for incising a stenosis in the vasculature of a patient includes a plurality of blade segments that are mounted and aligned on a base member. The base member, in turn, is mounted on the external surface of an inflatable angioplasty balloon. Accordingly, when the balloon is inserted into the vasculature of a patient, positioned across a stenosis and subsequently inflated, the blade segments form an effective cutting edge that effectively conforms to the surface of the stenosis. Due to this ability of the cutting edge to conform with the peaks and valleys of the stenosis, the stenosis can be incised to a substantially uniform depth.
In detail, to establish an effective cutting edge conformable to the surface of a stenosis, the blade segments are attached to the base member in a pattern that allows relative movement between adjacent blade segments. For the present invention, each individual blade segment is generally elongated and defines a blade axis in the direction of its elongation. Preferably, each blade segment is mounted on the base member and oriented with its blade axis either substantially parallel or substantially colinear with the blade axis of at least one other blade segment. Further, the distal portion of each blade segment is juxtaposed and preferably in contact with the proximal portion of the next closest blade segment (except for the blade segment at the extreme distal end of the pattern). As such, each blade segment is off-set from the next closest blade segment in the axial direction.
For the present invention, the base member is made of a resilient material, such as a thin strip of polyurethane material, which allows the base member to deform along with the surface of the angioplasty balloon during an inflation or deflation of the balloon. One side of the base member is preferably bonded to the external surface of the angioplasty balloon. For the present invention, an elongated angioplasty balloon, defining a balloon axis in the direction of elongation, is generally used. Preferably, the base member is also elongated and is mounted on the external surface of the balloon with the direction of base member elongation parallel to the balloon axis. For the present invention, the blade segments are mounted on the base member with each blade axis substantially parallel to the direction of base member elongation. Furthermore, each blade segment is formed with a taper section that creates a sharpened edge. Preferably, each blade segment is oriented on the base member with the sharpened edge of each blade segment lying substantially along a single continuous cutting line.
In operation, a catheter having an angioplasty balloon, base member and blade segments is inserted into the vasculature of a patient. The catheter is then advanced within the vasculature until the angioplasty balloon is positioned across a stenosis requiring treatment. For this purpose, a guidewire can be used to establish a mechanical pathway to assist the catheter to the treatment site. Next, the balloon is slowly inflated causing the external surface of the balloon, the base member and the blade segments to move outwardly together in a radial direction from the balloon axis until the blade segments contact the surface of the stenosis.
Upon contact with the surface of the stenosis, the sharpened edge of each blade segment cuts into the stenosis, creating an incision. Inflation of the balloon is then continued until the blade segments are effectively embedded into the stenosis. Eventually, the external surface of the balloon and the resilient base member contact and conform with the surface of the stenosis. Because the blades are segmented and positioned on the base member to allow relative movement between blade segments, the blade segments do not prevent the balloon and base member from conforming to the surface of the stenosis. Additionally, the relative movement between the blade segments allows the blade segments to form an effective cutting edge that conforms to the surface of the stenosis resulting in a nearly continuous incision of substantially uniform depth along the surface peaks and valleys of the stenosis.
After incision, the angioplasty balloon can be further inflated to dilate the stenosis, if desired. In any case, the angioplasty balloon is subsequently deflated to withdraw the blade segments from the stenosis. Once deflated, the balloon and blade segments can be repositioned for treatment of another stenosis or removed from the patient.